Method and apparatus for testing rotation-responsive delay devices

ABSTRACT

Arming delay-devices, suitable for delaying the arming of an artillery shell until it is well away from the gun by which it is fired, are tested in production by rotating each of them in a test stand and determining the number of turns of the device required for it to become armed.

I United States Patent 3,580,046

[72] Inventor Oliver F. Cheney [56] References Cited Philadelphia, Pa.UNITED STATES PATENTS No 1969 27,515 8/1943 Ferrone 73/5 Patented y2551971 2,353,436 5/1951 Brown... 73/167 [73] Assignee Delaware ValleyArmaments, Inc. f y Pmlce ML Laure] Twp, NJ Assistant ExaminerDenis E.Corr Attorney-l-lowson and l-lowson [54] METHOD AND APPARATUS FORTESTING 4 ROTATION-RESPONSIVE DELAY DEVICES 8 Claims, 6 Drawing Figs.

[52] U.S. Cl 73/5, ABSTRACT: Arming delay-devices, suitable for delayingthe 73/167 arming of an artillery shell until it is well away from thegun by [51] Int. Cl F42c 21/00 which it is fired, are tested inproduction by rotating each of [50] Field of Search 73/5, 167; them in atest stand and determining the number of turns of 89/6 the devicerequired for it to become armed.

Z30 25a UPT/COQL D. a. Z5 Z4 l: SENSOR M 1 ADJUST/151.1: Z/Z M PR5 SE7[45 NUMBER I Z s0u,4 c 5 Mara/P J 00/1/7904 LfiNTRflL Z/g/ *cwawr sroPLINE A 0. SUPPL Y METHOD AND APPARATUS FOR TESTING ROTATION- RESPONSIVEDELAY DEVICES BACKGROUND OF INVENTION This invention relates to methodand apparatus for testing rotation-responsive delay-devices,particularly arming delaydevices for use with shells.

It is known to employ delay-devices in explosive shells for the purposeof delaying, until a predetermined time after firing, the automaticarming of the shell which enables it to explode. In some cases thedelay-device may be utilized to cause such explosion to occur, but inother cases it is used as a safety device to prevent explosion of theshell until after the shell is well away from the gun by which it wasfired. For this purpose rotation-responsive delay-devices are knownwhich contain a mechanical time-delay mechanism controlling the armingof the device, which mechanism is set to its unarmed condition beforethe shell is put into the gun and responds to shell rotation afterfiring of the gun so as to move progressively toward its armed conditionduring the early portion of the flight of the shell.

The short arming times and high timing accuracies required in suchdelay-devices make it inevitable that there will be a significant spreadin operational characteristics of the delaydevice when it is made bymass-production techniques. It is also inevitable that an occasional oneof the mass-produced devices, if placed in a shell, would causetoo-early arming of the shell, or a too-late arming resulting in a dud"which would not explode because the delay-device had not become armed bythe time that shell explosion was desired. For the safety of personneland of the guns, it is important that the delay-device not arm itselftoo early, and obviously the firing of duds preferably is to beprevented also. From the economic viewpoint of the producer, it is alsooften important to avoid the delivery to a buyer of even one earlyorlate-arming delay-device in a batch, since a random checking of thedelay-devices or of the complete shell assemblies by the buyer whichresults in finding a defective device in a batch may well result inrejection of the entire batch. For all of these reasons it is desirableto subject each delay-device to a simulated performance check before itis delivered to the customer.

The present invention is concerned primarily with a method and apparatusfor performing such checks or tests. Previously such tests have beenmade by attempting to rotate the delaydevice exactly at a specifiedfixed rate of rotation for a specified brief time period and sensingwhether the device has armed itself in the specified time.

A number of difficulties have been encountered with such a testprocedure which have made it difficult to perform accurately andfrequently over long periods. First, it requires very accuratemaintenance of the rotation frequency at the prescribed value throughoutthe test interval, combined with accurate time measurement or accuratecontrol of the duration of the test interval. Since the duration of thetest is itself typically short, e.g. 0.8 second, the time period duringwhich the rotational speed rises from zero to the specified constantspeed must be very short and preferably constant for all tests in orderto achieve accuracy and reliability of measurements. Ideally therotational speed is a step function, rising instantaneously from zero toexactly the prescribed test speed and remaining constant at the lattervalue throughout test; in some tests it is also necessary to stop therotation nearly instantaneously to obtain accurate results. In anypractical system such nearly instantaneous starting and/or stopping isdifficult to provide, and departures from the ideal situation have beenfound to result in test inaccuracies of practical importance. It isparticularly difficult to provide accurate test performance repeatedlyover long periods of time, especially in view of the unusual stressesproduced on the equipment by sudden startup and/or stopping and in viewof unavoidable changes in the equipment due to wear.

A possible alternative for avoiding problems of rapid rotational startupand/or stopping is to place the delay-device in rotation at the desiredangular velocity while it is unarmed and before it is actuated, toactuate it only after it has come up to the specified speed so that itwill then proceed toward its armed condition, and to measure theinterval between such actuation and the time at which the armedcondition is achieved. This requires a special arrangement for producingand sensing the initial actuation of the device while the device isrotating at a high rate, and again requires that the speed of rotationbe held constant throughout the test interval.

Accordingly, it is an object of the invention to provide a new anduseful method and apparatus for the testing of delaydevices.

Another object is to provide such method and apparatus which is ofimproved accuracy and reliability, especially over long periods ofrepeated use.

Another object is to provide such method and apparatus whichis simpleand convenient to operate.

A further object is to provide such method and apparatus which does notrequire accurate measurement or control of rotation rate or testduration.

SUMMARY .OF INVENTION We have found that in certain types ofdelay-devices which operate in response to rotational motion thereof,the time required for the device to change from its initial unarmedcondition to its armed condition (i.e. the time-to-arm) is inverselyproportional to its angular velocity of rotation, at least over asubstantial range of angular velocities. That is, the faster the deviceis rotated the faster it advances toward its armed condition and theshorter the time-to-arm 1, This relation is expressed by the followingequation:

where w is the angular velocity of the delay-device about its axis and Kis a constant characteristic of the delay-device. Such a characteristichas been found typical, for example, in delay-devices of the type usinga centrifugally operated runaway escapement.

In accordance with the invention there is provided a method andapparatus for the testing of such delay-devices having a time-to-arminversely proportional to the rate of rotation thereof, in which thecriterion or measurement utilized in testing is the number of turns ofrotation of the fuse required to produce arming thereof, i.e. theturns-to-arm, rather than the time-to-arm at a specified rotation rate.It has been found that, with this method and apparatus of the invention,the rotational speed may vary substantially during test without reducingthe accuracy of the test, thereby avoiding the necessity for producingstep-changes in rotational rate and for controlling accurately the rateof rotation. Preferably the delay-device is placed in its unarmed'condition while at rest and is then rotated at a rate subject tovariation, the number of turns being counted and used as the testcriterion. For example, in one preferred embodiment the unarmed fuse isplaced into rotation, the turns are counted, the time at which armingoccurs is sensed, and the number of accumulated turns which have beenperformed, from the beginning of rotation up to the time of arming, isdetermined. The resultant turns-to-arm figure is then utilized as thecriterion of an acceptable fuse. In an alternate embodiment, apredetermined number of turns less thanthat for which the fuse is tobecome armed are applied to the fuse, rotation is then stopped, and thearmed or unarmed condition of the fuse is observed; if the fuse hasbecome armed in this time it is rejected. Similarly, a predeter minednumber of turns corresponding to the desired maximum range-to-arm may beapplied to' the delay-device, and those fuses which are not armed bythis number of turns may be rejected we duds."

During these tests the speed of rotation is not critical, and startupand arresting may be at relatively slow rates. Ac-

cordingly the principal sources of the difficulties outlined above fortime-to-arm tests are avoided, and accurate, reliable, repetitivemeasurements made possible in mass production over long periods of time.

Such tests in terms of turns-to-arm are not only easier to make and moreaccurate than time-to-arm tests, but are also meaningful with respect tothe end use to which the delaydevice is to be put. To a firstapproximation, the range-to-arm R, of a delay-device obeying equation(1) above is substantially equal to T /G where t,, is the turns-to-armand G is a constant characteristic of the geometry of the gun (includingits barrel rifling) from which the shell is to be fired. Hence for anygun of given geometric characteristics, the range-to-arm R isdetermined'directly by the turns-to-arm T substantially independently ofthe muzzle velocity. In this respect the situation is somewhat analogousto rollinga ball along a flat surface so that its rate of rotation isproportional to its forward velocity; the number'of turns made by theball in travelling a given distance will be independent of its forwardvelocity, and the numberof turns it makes in travelling to any positionwill therefore be a measure of the distance it has travelled. Similarlyfor a shell fired from a given gun having predetermined barrel riflingwhereby the rate of rotation of the shell upon exit from the gun issubstantially proportional to muzzle velocity, the number of turns madeby the shell in flight is a measure of the range through which it hastravelled, and the number of turns in flight required to arm thedelay-device (T,,) is therefore a measure of the range at which armingoccurs (R forthat or a similar gun.

When using the tums-to-arm criterion of the invention, the rotationalstartup and/or slowdown speed pattern is not important, and there istherefore no need for instantaneous startup or stopping and noneed tomeasure or to maintain the rotational speed constant during test.Because of this, substantial improvements in accuracy and reliability oftesting have been realized. I

BRIEF DESCRIPTION OF FIGURES Other objects and features of the inventionwill be more readily understood from a consideration of the followingdetailed description taken with the accompanying drawings in which:

FIG. I is a fragmentary side view, with parts broken away, showing theposition in a conventional shell of a delay-device of the type suitablefor testing by the method and apparatus of the invention;

FIG. 2 is an end view showing one face of the conventional delay-deviceof FIG. 1, with its cover plate removed;

FIG. 3 isa schematic diagram showing one form of test apparatus inaccordance with the invention;

FIG. 4 is a schematic diagram showing another form of apparatus inaccordance with the invention;

FIGS. 5 and 6 are graphical representations to which reference will bemade in explaining the operation of the apparatus of FIGS. 3 and 4respectively.

DETAILED DESCRIPTION Referring now to the specific embodiments of theinvention shown in the drawings by way of the example only, FIG. 1illustrates an explosive shell 10 containing as a component thereof anarming delay-device 12 of a type suitable for testing by the method andapparatus of the invention. The shell may be of the type comprising amain body portion 14 containing a main explosive charge intended toexplode in response to impact of the firing pin 16, against the groundor similar object. Actuation of firing pin 16 by impact detonates theadjacent detonator 17 to produce an impulse which, when the system isfully armed, travels along the interior of a flash tube 20 to the frontsurface of the delay-device 12 and through a central opening in thedelay-device 12 to a detonator 21, which in turn explodes to detonate abooster-charge pellet 22 and, in turn, the main explosive chargecontained in the rear of the shell behind the booster cup 22A.

However, arming delay-device 12 has an unarmed condition in which thecentral opening through it is blocked and detonator 21 not aligned withbore 20, and contains a timing mechanism responsive to rotation of theshell to move progressively toward its armed position in which thecentral opening is unblocked and detonator 21 aligned withbore 20. Inuse, the arming delay-device 12 in its unarmed condition is installed inthe shell before the shell is to be used and, when the shell is fired,the rotation of the shell due to the barrel rifling causes the armingdelay-device to move progressively toward its armed condition and toreach the armed condition when the shell is at an appropriate distanceaway from the gun.

Typically the shell assembly may also comprise an auxiliary delayplunger assembly 23 which closes off communication between flash tube 20and delay-device 12 until the shell begins to rotate in the gun, atwhich time assembly 23 is promptly actuated centrifugally to open thepath to delaydevice 12. Also sometimes employed is an interrupter.assembly 24 which can be manually adjusted either to open the centralbore from the flash tube to the assembly 23, or to divert the explosiveimpulse through a parallel path (not shown) thereby to introduce afurther fixed delay in explosion of the shell.

The above-described shell assembly and delay devjce 12 may be of knowntypes, such as those used in conventional army artillery shells. In thepresent case the delay-device 12 is of a type in which the time for itto become armed is inversely proportional to its rate of rotation, acharacteristic which has been found to exist in most centrifugallyoperated delay mechanisms and particularly those of the runaway.escapement type.

FIG. 2 illustrates the important operative components of one such knowntype of arming delay-device 12. since such delay-devices and timingmechanisms are well known in the art, all of the structural details arenot shown or described in detail. In general, a segmentally toothedrotor gear assembly 40 is mounted for rotation on the body 42 of thedelay-device 12, by means of a rotor shaft 44 radially displaced fromthe shell axis 47. The rotor gear assembly 40 carries the detonator 21behind it, and is'appropriately weighted so that its center of gravityis displaced from the axis of rotor shaft from the shell axis- 47, andat least initially is also displaced from that shell diameter whichpasses through the rotor axis and the shell axis. Accordingly, uponrotation of the shell about axis 47, the center of gravity of rotor gearassembly 40 tends to move toward its radially outermost position,thereby exerting a torque on the rotor gear assembly about the rotoraxis.

For safety purposes, the rotor gear assembly 40 is initially held in itscompletely unarmed position (as shown) bya pair of rotor detents 50 and52, which engage corresponding depressions in the edge of the rotor gearand are normally spring-biased into this position by means ofcorresponding detent springs 56 and 58 respectively. When the shell isfired, the first small fraction of a revolution of the shell issufficient to cause the rotor detents to pivot outwardly about theirrespective detent shafts 64 and 66 and thus free the rotor gear assembly40 for progressive rotation about its shaft axis; this typically occursat about 1,000 to 2,000 rpm.

In the example shown in FIG. 2, rotor gear assembly 40 then responds toshell rotation to rotate progressively further in the counterclockwisedirection, with respect to body 42, about an axis through rotor shaft44. The teeth of rotor gear assembly 40 thereby drive the pinion of thefirst gear-and-pinionassembly 60, the support shaft 61 of which assemblyis rotatably mounted on body 42. The resultant rotation ofgear-andpinion assembly 60 drives a second gear-and-pinion assembly 64,with which it engages; the latter gear-and-pinion assembly then drivesthe pinion of the escape wheel and pinion assembly 68, the support shaftfor which is also rotatably mounted on body 42. The escape wheel of theassembly 68 is toothed in appropriate manner to engage the balance pins72 and 74 of the pivoted balance 76, and to cause the latter balance tooscillate back and forth rotationally about a pivot 77.

The above-described mechanism is commonly known as a centrifugallyoperated runaway escapement, and responds to rotation of the shell insuch manner that the arming time required for the detonator 21 to movecounterclockwise from its initial unarmed position into an armedposition coaxial with the shell axis 47 (shown dotted at 21A) isinversely proportional to the rate of rotation of the shell. There are avariety of mechanisms which exhibit this characteristic, and itsexistence may be determined by analysis or simply by measurements of thetimes required for arming at different rates of rotation of themechanism.

The mechanism of FIG. 2, it will be understood, would normally becovered on its front face with a cover plate having a central aperturecoaxial with the shell axis 47, thereby to protect the mechanism.Detection of the existence of the armed or unarmed condition isconveniently enabled by the fact that, in the unarmed condition, themetal of the surface of the rotor gear assembly 40 is visible at thecenter of the shell axis, and may for example be of reflective brass;the visible end of the detonator 21, on the other hand, may be a dullred so that when the delay-device becomes armed the dull red color isvisible at the shell axis, through the central opening in the coverplate. This facilitates both visual and optical sensing of the armed andunarmed conditions of the mechanism.

There will now be described in detail the method and apparatuspreferably utilized in accordance with the invention to testdelay-devices of this class, namely those in which the time for armingis inversely proportional to the rate of rotation thereof.

Referring now to FIG. 3, the apparatus illustrated therein is suitablefor applying a specific predetermined number of turns of rotation to anarming delay-device, for example to determine whether it arms itself toosoon. In essence, the minimumacceptable number of turns-to-ann is firstdetermined, and the apparatus shown then serves to provide this numberof turns to each delay-device to be tested, after which the delay-devicecan be examined to determine whether it has armed itself during thetest. If it has, it is rejected because of its too-early armingcharacteristic. Those devices not becoming armed during the test aredeemed acceptable, at least with respect to their minimum arming-timecharacteristics.

In the FIG. 3 embodiment, an upright cuplike spinner 200 is designed toreceive the delay-device 12, the bottom of the spinner being providedwith an upright pin 201 which extends into a corresponding bore in thelower end of delay-device 12 so that spinning of spinner 200 causesdelay device 12 to spin along with it at the same rate. A drive shaft202 is operatively connected to spinner 200, and is itself supported forrotation on appropriate bearings (not shown). A driven pulley 206 at theopposite end of the drive shaft 202 is coupled by means of a belt 208 toa driving pulley 210, which is rotated by electric motor 212 thereby torotate drive shaft 202. Electrical power for driving motor 212 issupplied from an AC supply line 216 by way of a suitable motor controlcircuit 218 which responds to operation of a start control 220 to startoperation of the motor and which responds to application of a current tostop terminal 222 thereof, over line 224, rapidly to arrest motion ofthe motor. There are many types of motors which may be utilized for thispurpose, although for convenienceand to avoid problems of brush life itis preferred to use an AC motor, and to apply a direct current throughthe normal AC windings in the direction to stop the motor rapidly.

Drive shaft 202 is provided with a decimal disc 230 which rotates withshaft 202 and contains around its outer periphery a plurality (in thiscase of optically distinguishable transverse regions such as 232; forexample, the region between the elements 232 may be black and theelements such as 232 may be of bright reflecting material. An opticalsensor 236, containing a conventional lens and photocell arrangement, ispositioned so as to sense the passage of each of the elements 232through a predetermined position adjacent the sensor, and to produce anelectrical pulse in response to each such passage. In this way, l0pulses are produced by the optical sensor 236 for each full revolutionofdrive shaft 202.

The electrical output of the optical sensor 236 is passed through aconventional direct-current amplifier 238 to a counter and comparisonunit 240. Unit 240 comprises a pulse counter 242 supplied with thepulses from DC AMPLIFIER 238 and effective to count them, beginning fromthe time at which the motor is started by operation of the startercontrol 220. A reset line 245 is preferably connected from the startcontrol 220 to the reset input of counter 242 so as to reset it at thestarting of each new testing operation.

Circuit 240 also comprises a comparator 244 supplied with the signalfrom counter 242 and from an adjustable preset number source 246, whichcan be manually adjusted to apply to comparator 244a signalrepresentative of a chosen number corresponding to the number of turnswhich are to be applied to the delayalevice 12 during test. Comparator244 compares the count from counter 242 with the number informationsupplied form source 246 and, when these two numbers become equal,produces an output current on line 224 to motor control circuit 218 toeffect arresting of the rotation of motor 212. Because of delays in themotor control circuit and in the motor braking, the number representedby the signal from number source 246 is typically smaller than the turnsto be applied by the number of turns made during the relay-operating andbraking times.

Each of the variouselements of the circuit of FIG. 3 may be constructedin accordance with known conventional practice, and hence the detailsthereof need not be described herein. It is sufficient to point out thatin view of the characterization of the various elements and theiroperation set forth above, it will be apparent to one skilled in the artthat the apparatus of FIG. 3 applies a predetermined number of turns tothe delay-device 12 upon operation of the start control 220 by anoperator, and that the criterion utilized in the operation of theapparatus is the number of turns made by the delay-device l2, and notthe time for which it runs; furthermore, no special control ormeasurement is provided for maintaining a particular frequency ofrotation of delay-device 12 during the test, and startup times are notcritical.

FIG. 4 illustrates another embodiment of apparatus for testing of armingdelay-devices such as 12. In this case sufficient turns are applied toassure arming of those delay-devices having acceptable characteristics,and an indication is provided of the number of turns required to arm theparticular delaydevice being tested. The delay-device 12 is againmounted in an appropriate cuplike spinner 310 for rotation by motor 312by way of belt 313 and drive shaft 314, the operation of the motor beingcontrolled by a suitable motor control circuit 316 supplied with ACsupply current over line 318. A toothed ring 320 of magnetic material isprovided at the bottom of spinner 310, and rotates with drive shaft 314.The'teeth of ring 320 cooperate with a magnetic pickup 322 to produceelectrical pulses from magnetic pickup 322 each time one of the teethpasses a predetermined position adjacent the pickup; suitable forms forsuch a pickup, including types utilizing electromagnets, are well knownin the art. Electrical pulses from pickup 322 are thereby applied to thecount input of a pulse counter 324 when spinner 310 has been placed inrotational motion by operation of the motor start control 329.

The cylindrical detonator 21 in the delay-device 12 is provided with anupper surface which is optically differentiable from the surroundingupper surface of the delay-device 12, as previously described. That is,in this example it is provided with a dull red coating so that thecentral aperture in delaydevice 12 is closed by a shiny metallic surfacewhen the device is unarmed and is closed by a dull red surface when itbecomes armed. This provides a convenient method for optically detectingthe armed condition of the device.

More particularly, a suitable light source 336, including the usual lampand lens system, directs illumination upon the center of the uppersurface of delay-device 12, the reflection of this light being sensed'byan optical sensor 338, which may include the usual lens arrangements andphotocell. devices suitable for such purposes. Optical sensing unit 338then supplies a relatively large current to photocell amplifier 340 whendelay-device 12 is unarmed but, when, it becomes armed, the resultantreduction in reflected light from the dull-red end of the detonator 21will cause an abrupt drop in the current to the photocell amplifier.Accordingly, a recognizable pulse is produced by photocell amplifier 340when the delay-device becomes armed. Alternatively, the change in hue atthe center of the delay-device due to arming may be sensed by includingone or more color-selective filters in the optical-sensing means, so asto sense changes in reflected light of a selected color (e.g. red) or tosense and compare two colors of reflected'light (e.g. red and green) forthe armed and unarmed conditions.

The latter output pulse from photocell amplifier 340 is supplied to stopterminal 323 of counter 324 to stop the abovedescribed counting of theturns indicating pulses from magnetic pickup 322. Counter 324 thenindicates the number of turns of the delay-device 12 required for it tobecome armed. This information may be displayed in conventional mannerby counter 324 so as to enable visual reading thereof by an operator.However, in the present embodiment further apparatus is provided toproduce an automatic optical indication of whether the turns-to-arm iswithin or outside a preset accepted tolerance range.

More particularly, the count produced by counter 324 is supplied to acomparator logic circuit 328, to which there is also supplied numericalinformation from an adjustable upperlimit number source 330 and anadjustable lower-limit number source 332. The latter two sources ofnumerical information may be adjusted by the operator to provide anydesired upper and lower limits defining an acceptable tolerance rangefor the turns-to-arm of the delay-device.

Comparator logic circuit 328 operates, in response to a control pulsefrom photocell amplifier 340 delivered over line 339, to compare thecount achieved by counter 324 with the upper and lower limitsestablished by sources 330 and 332. In this embodiment, comparator logiccircuit 328 produces an output current from output terminal 350 thereofwhen, and only when, the count finally achieved by counter 324 liesbetween the upper and lower limits established by sources 330 and 332.This output current passes through an accept" lamp 354 to the motor-stopcontrol terminal 356 of motor control circuit 316, so that the motor isthereby automatically stopped and the accept" lamp illuminated toindicate to the operator that the unit is acceptable. On the other hand,if the count achieved by-counter 324 is outside the range established bythe upper and lower limits of sources 330 and 332, an output current isproduced from output terminal 362 of comparator logic circuit 328, whichpasses through the reject lamp 364 to the motor stop terminal 356. Undersuch conditions, the reject lamp is illuminated instead of the accept"lamp, and the operator is thereby warned that an unacceptable unit hasbeen tested; the motor is at the same time automatically stopped inpreparation for testing of the subsequent unit.

Resetting of the counter may be provided automatically in response tooperation of the start control 329 by way of an appropriate reset line370 connected to the reset terminal of counter 324.

Again, as in the case bf the embodiment of FIG. 3, the rate of rotationof the delay-device l2 and the duration of its rotation are notcritical, since it is merely the total number of turns provided which isused as the criterion for acceptance or rejection of the device, andneither startup, stopping nor speed of running between start and stopare in any way critical.

Considering now FIG. with particular reference to the operation of theapparatus of FIG. 3, there is shown therein a graph in which ordinatesrepresent revolutions per minute of the spinner 200 and of thedelay-device 12 contained therein, and abscissae represent time inmilliseconds measured from the time t at which rotation of the spinneris started. When the speed has risen to about 1,500 rpm, the speed leveld is reached at which the detents 50 and 52 of FIG. 2 move outwardly torelease the rotor gear assembly 40 and thereby actuate the delay-deviceso that it immediately begins to move toward its armed position. Thefull test speed of 3,000 rpm. is reached in about 60 milliseconds and iscontinued for another 650 milliseconds, at which time braking of themotor 212 will begin; braking of the motor will be substantiallycompleted at about 800 milliseconds, or 0.8 second after the motor wasstarted.

Using prior-art test procedures, the operation shown in FIG. 5 wouldrepresent an attempt to rotate the delay-device at a test speed of 3,000r.p. m. for a period of 650 milliseconds. For such a test to besatisfactory, the test speed would have to be accurately controlled,during repetitive tests and over long periods of time, at the exactvalue of 3,000 rpm, with resultant complexity, expense an inherentsusceptibility to at least some degree of error. In addition, even ifthe speed were so controlled during the 650 millisecond interval,rotation during the finite startup and stop intervals would produceadditional arming motion of the delay beyond that intended to be appliedduring the 650 millisecond interval. Such motion occurs upon startup,between the time when the speed has reached the detent-release speed dand the time t, at which the test speed is achieved, and also occursupon arrest, between the time t;, when braking starts and the time twhen the motor actually stops. The effects on time-to-arm of thesestartup and stop intervals will vary between different types of testequipment, between different embodiments of the same type of equipmentand, importantly, between different times and con ditions of operationof the same test equipment because of wear, aging and changes inenvironmental conditions. For these reasons also, such prior art testingprocedures and apparatus involve substantial inaccuracies in measurementand/or additional expense in construction and maintenance of theapparatus.

With the method and apparatus of the invention on the other hand,counter 242 counts the total number of turns applied to the delay-devicefrom the initial startup time t to the final arrest time t.,, and thecomparator 244 operates to stop the motor at the appropriate time so asto apply the desired total number of turns to the delay-device. Forexample, in terms of turns, rotation of the delay-device is initiated atthe time t increases in about one-half turn to the detent-release leveld, achieves maximum velocity at the time I, after a total of about twoturns, continues for an additional 30 turns at which point comparator244 puts out a stop signal, and continues for an additional 2% turnswhile the relays in the motor control circuit 218 respond to the stoppulse to begin arrest of motor 212. An additional two turns maytypically be required to bring the motor to a complete stop. Thus, inthe assumed practical embodiment, about 4% turns occur after thecomparator 244 produces its stop signal, so that if, as in the exampleshown, 36 /2 turns are to be applied, the adjustable preset numbersource 246 would be adjusted to the number 32; or, the system can bearranged so that the latter number source is adjusted to equal the totalturns desired 36 /2) and the comparator 244 internally arranged so as toeffectively subtract 4% turns from this number and thereby produces anoutput stop pulse when counter 242 reaches the 32-turn count.

With this operation in accordance with the invention, the criterion isthe total turns applied to the delay-device, and the manner in which thespeed or rotation varies during the test period is therefore notcritical; in particular, the exact form of startup speed-characteristic,and the exact value of the rotational speed between the startup andarrest intervals, are not critical and. may be varied withoutsubstantially altering the accuracy of the test. Of course, as inpreviously described operations, account should be taken of the factthat the detents prevent the delay-device from responding to rotationduring the first half-tum of the device. With any reasonably rapid motorstartup characteristic, this does not introduce any substantial error inthe measurements; however, it should be recognized that, in theoperation shown in FIG. 5, the complete delay-device has been suppliedwith 36 /2 turns, but the escapement mechanism has been supplied withonly 36 turns.

Referring now to FIG. 6 with particular regard to the operation of theapparatus of FIG. 4, again ordinates represent revolutions per minute,but in this case abscissae represent turns applied to the delay-deviceabout its axis. it is assumed in this example that the general form ofthe pattern of rotational motion applied to the spinner 310 is similarto that discussed with reference to FIG. 5, except that the rotation isapplied for a longer time and through a greater number of turns, so asto assure that all acceptable delay-devices will have been armed beforethe motor 312 is arrested. In this example it is assumed that, deviceswhich arm themselves between 34 and 46 turns areacceptable, and thoseoutside this range are not. ln the example shown, the device is assumedto arm itself at 40 turns, which stops counter 324 and actuatescomparator logic circuit 328. The number 40 for the tums-to-arm can bevisually read on counter 324, and the comparator and logic circuitdetermines whether this number is between the minimum and maximumallowable limits for test; if so, the comparator and logic circuit thenproduces an'output signal through the accept lamp 354 to light it and toinstitute arresting of motor 312 preparatory to testing of the nextdelay-device. If the photoelectrically measured tums-to-arm is less than34 or greater than 46, the comparator and logic circuit 328 will applyits output through reject lamp 364, indicating an unacceptable device,and will again arrest the motor 312.

Again, in connection with the procedure described with reference to FIG.6, since tums-to-arm are sensed and used as the criterion of test,variations in startup of the motor, in the rate of rotation during themain portion of the test interval, and in the arresting operation do nothave a significant effect upon the accuracy of results and hence are notcritical.

It will therefore be appreciated that there has been provided method andapparatus for testing delay-devices of the type in which the time delayis inversely proportional to the rate of rotation thereof, wherebyinaccuracy, complexity, difficulties of maintenance, and cost aresubstantially reduced by use of a tums-to-arm criterion.

While the invention has been described with particular reference tospecific embodiments thereof in the interest of complete definiteness,it will be understood that it may be embodied in a variety of otherdiverse fonns differing substantially from those specifically shown anddescribed without departing from the scope and spirit of the inventionas defined by the appended claims.

lclaim:

l. The method of testing the action of an arming delaydevice for aprojectile of a type to be fired flom a rifled barrel with imparts spinto said projectile, said delay-device comprising a centrifugallyoperable element supported on a body which spins with said projectile,said element being responsive to centrifugal forces generated byspinning of said body to move with respect to said body from an initialunarmed position to asecond armed position in a time inverselyproportional to the rate of said spinning, said method comprisingplacing said element in its unarmed position, spinning said body at arate which is subject to variation, counting the number of turns made bysaid body during said spinning, and selecting said delay-device assatisfactory on the basis of the number of said turns required for saidelement to move from said unarmed to said armed position thereof.

2. The method of claim I in which said spinning is continuedsufficiently long to cause said element to move to said armed position,and comprising the steps of detecting the time at which said elementreaches said armed position and detecting the number of said turns whichhave been made at the time when said element reaches said armedposition.

3. The method of claim 1, comprising the step of arresting said spinningafter a predetermined member of said turns have been made, and thendetecting whether said element has reached said armed position.

4. Apparatus for testing the action of an arming delaydevice for aprojectile of a type to be fired from a rifled barrel which imparts spinto said projectile, said delay-device comprising a centrifuga llyoperable element supported on a body which spins with said pro ectile,said element being responsive to centrifugal forces generated byspinning of said body to move with respect to said body from an initialunarmed position to a second armed position in a time inverselyproportional to the rate of said spinning, said apparatus comprising:

means for spinning said body during an interval including a period inwhich the rate of said spinning is subject to variation; means forcounting the number of turns made by said body during said spinning; and

means actuated by said counting means for enabling determination of thenumber of said turns which have been made by said body;

said actuated means comprising means for arresting said spinning after apredetermined number of said turns.

5. Apparatus for testing the action of an arming delaydevice for aprojective of a type to be fired from a rifled barrel which imparts spinto said projectile, said delay-device comprising a centrifugallyoperable element supported on a body which spins with said projectile,said element being responsive to centrifugal forces generated byspinning of said body to move with respect to said body from an initialunarmed position to a second armed position in a time inverselyproportional to the rate of said spinning, said apparatus comprising:

means for spinning said body during an interval including a period inwhich the rate of said spinning is subject to variation;

means for counting the number of turns made by said body during saidspinning; and

means actuated by said counting means for enabling determination of thenumber of said turns which have been made by said body; said apparatuscomprising means .for sensing, and producing a signal representative of,the time at which said element reaches said armed position, and in whichsaid actuated means comprises means for terminating counting of saidturns in response to said signal. 6. Apparatus for testing a fuse havingan arming time inversely proportional to the rate of rotation thereofabout a predetermined axis therein, comprising:

means for rotating said fuse about said axis at a rate and for a timesufficient to operate said fuse from its unarmed condition to its armedcondition;

means for sensing the time of occurrence of said armed condition and forproducing a first signal representative of said time;

means for counting the number of turns of said fuse during saidrotation; and

means responsive to said first signal for terminating the operation ofsaid counting means when said fuse becomes armed.

7. The apparatus of claim 7, for testing of a fuse having a mechanicalelement movable during operation to a predetermined position indicativeof the armed condition of said fuse, in which said sensing meanscomprises optical-sensing means for detecting the time at which saidelement attains said predetermined position.

8. The apparatus of claim 7, in which said means for rotating said fusecomprises motor means operatively connected to said fuse.

1. The method of testing the action of an arming delay-device for aprojectile of a type to be fired from a rifled barrel with imparts spinto said projectile, said delay-device comprising a centrifugallyoperable element supported on a body which spins with said projectile,said element being responsive to centrifugal forces generated byspinning of said body to move with respect to said body from an initialunarmed position to a second armed position in a time inverselyproportional to the rate of said spinning, said method comprisingplacing said element in its unarmed position, spinning said body at arate which is subject to variation, counting the number of turns made bysaid body during said spinning, and selecting said delaydevice assatisfactory on the basis of the number of said turns required for saidelement to move from said unarmed to said armed position thereof.
 2. Themethod of claim 1 in which said spinning is continued sufficiently longto cause said element to move to said armed position, and comprising thesteps of detecting the time at which said element reaches said armedposition and detecting the number of said turns which have been made atthe time when said element reaches said armed position.
 3. The method ofclaim 1, comprising the step of arresting said spinning after apredetermined member of said turns have been made, and then detectingwhether said element has reached said armed position.
 4. Apparatus fortesting the action of an arming delay-device for a projectile of a typeto be fired from a rifled barrel which imparts spin to said projectile,said delay-device comprising a centrifugally operable element supportedon a body which spins with said projectile, said element beingresponsive to centrifugal forces generated by spinning of said body tomove with respect to said body from an initial unarmed position to asecond armed position in a time inversely proportional to the rate ofsaid spinning, said apparatus comprising: means for spinning said bodyduring an interval including a period in which the rate of said spinningis subject to variation; means for counting the number of turns made bysaid body during said spinning; and means actuated by said countingmeans for enabling determination of the number of said turns which havebeen made by said body; said actuated means comprising means forarresting Said spinning after a predetermined number of said turns. 5.Apparatus for testing the action of an arming delay-device for aprojective of a type to be fired from a rifled barrel which imparts spinto said projectile, said delay-device comprising a centrifugallyoperable element supported on a body which spins with said projectile,said element being responsive to centrifugal forces generated byspinning of said body to move with respect to said body from an initialunarmed position to a second armed position in a time inverselyproportional to the rate of said spinning, said apparatus comprising:means for spinning said body during an interval including a period inwhich the rate of said spinning is subject to variation; means forcounting the number of turns made by said body during said spinning; andmeans actuated by said counting means for enabling determination of thenumber of said turns which have been made by said body; said apparatuscomprising means for sensing, and producing a signal representative of,the time at which said element reaches said armed position, and in whichsaid actuated means comprises means for terminating counting of saidturns in response to said signal.
 6. Apparatus for testing a fuse havingan arming time inversely proportional to the rate of rotation thereofabout a predetermined axis therein, comprising: means for rotating saidfuse about said axis at a rate and for a time sufficient to operate saidfuse from its unarmed condition to its armed condition; means forsensing the time of occurrence of said armed condition and for producinga first signal representative of said time; means for counting thenumber of turns of said fuse during said rotation; and means responsiveto said first signal for terminating the operation of said countingmeans when said fuse becomes armed.
 7. The apparatus of claim 7, fortesting of a fuse having a mechanical element movable during operationto a predetermined position indicative of the armed condition of saidfuse, in which said sensing means comprises optical-sensing means fordetecting the time at which said element attains said predeterminedposition.
 8. The apparatus of claim 7, in which said means for rotatingsaid fuse comprises motor means operatively connected to said fuse.